Remote follow-up automaticity with intelligent data download restrictions

ABSTRACT

An implanted device is equipped with a flag that indicates to a remote monitoring unit that an event such as a patient medical emergency or device failure has occurred. The remote monitoring unit is configured in some embodiments to maintain a low power communication link with the implanted device when they are within range. When the flag indicates an event has occurred, the remote monitoring unit quickly downloads sensed data collected by the implanted device and transfers it over a network so that it can be utilized by a medical practitioner. The remote monitoring unit is further configured in some embodiments to query the implanted device at regular intervals. The remote monitoring unit may read a subset of the data stored by the implanted device and, based on that data, determine whether to complete a full or partial download.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of copending U.S. patent application Ser.No. 11/838,781, filed Aug. 14, 2007, titled “Remote Follow-UpAutomaticity with Intelligent Data Download Restrictions.”

FIELD OF THE INVENTION

The present invention generally relates to an implantable pulsegenerator or implantable cardiac stimulation devices. The presentinvention more particularly concerns a system for efficientlydownloading data collected by an implanted pulse generator to a remotemonitoring unit.

BACKGROUND OF THE INVENTION

Implantable cardiac pulse generators such as implantable cardiacstimulation devices (IPGs) may take the form of implantablecardioverter-defibrillators that utilize unique and rapid stimulationrates or high energy shocks to treat accelerated or chaotic rhythms ofthe heart in an effort to restore a normal heart rhythm. IPGs can alsoinclude pacemakers that provide low voltage stimulation to regulate theheart rate in the setting of a bradycardia. In addition to providingtherapeutic stimulation, these IPGs include sensing circuits that senseelectrical signals generated by the heart indicative of cardiac activityand memory device to store these sensed signals and data. IPGs aretypically also configured to transmit stored signals and data toexternal devices or programmers in order to aid a diagnosis by aphysician or clinician. For the purpose of this patent, an IPGrepresents any implantable medical device capable of monitoring one ormore physiologic functions and/or delivering therapy. As such, inaddition to cardiac pacemakers and cardioverter-defibrillators which arewell established in the art, this also includes neurologic stimulationdevices, gastric stimulation devices, implantable monitors includingcardiac monitors, glucose monitors and others.

Historically, the transfer of data from the IPG to the programmer orother device was performed either in the hospital or the physician'soffice. Increasingly, the transfer of this data from the implantabledevice to an external device accessible by a physician is done inlocations outside of a clinic, hospital, or other traditional medicalsetting. For example, a patient having an IPG may also have a remotemonitoring unit (RMU) in their home that automatically communicates withthe IPG to wirelessly download data acquired by the IPG. Data acquiredby the RMU may be transferred over a network to a remote server so thatit is accessible to a physician or a clinician at a remote medical site.

However, RMUs fail to handle many dangerous events and the generaltransfer of data efficiently. For example, a typical RMU located in apatient's home may operate by downloading information obtained andstored on the IPG at regular intervals. However, an event (e.g., apatient's medical condition) may occur shortly after the previousdownload and this event would not be acquired by the system until thenext scheduled download. In the case that the event represents a problemwith the IPG or a patient emergency, the proper medical professional maynot be alerted quickly when another scheduled download is not for sometime. This may put the patient at risk when a problem is beingexperienced and they are unable to either detect or inform a physicianor emergency medical technician themselves.

One current solution to this problem used with some RMUs is to increasethe frequency at which data transfers occur. If the RMU downloadsinformation from the IPG more frequently, then the average time betweenan event and data collection will decrease. However, the frequenttransfer of information from the implanted device and the monitoringsystem may reduce the battery life of the IPG because of the increasedpower requirements of the more frequent wireless transfer ofinformation. When there is no meaningful event to report, this excessivetransfer of information is inefficient and needlessly reduces batterylife as well as potentially overloads the memory of the server or theRMU. Additionally, the drain on the battery becomes worse as the timebetween transfers decreases, forcing a trade-off with this solutionbetween device life and safe monitoring of the patient. Even incircumstances where the download frequency has not been increased,valuable battery power may be used to implement preplanned downloadsthat contain information of limited value. Generally, implantablecardiac stimulation devices that have download capability are programmedto download at regular intervals. However, some patients may haverelatively stable cardiac conditions such that the information beingdownloaded provides no real new information to the treating physician.In this circumstance, battery power is being consumed to provideinformation of limited value. Conserving battery power is, of course, ofgreat concern with implanted devices as IPG replacement due to batterydepletion typically involves an invasive medical procedure.

Thus, there is a need in the art for a system that more efficientlyprovides information obtained by an IPG to a RMU. There is a need in theart for a system that is able to quickly alert a physician or emergencymedical technician to the occurrence of a major event, while limitingdownloads and drain on battery power when the downloaded informationdoes not warrant the power expense.

SUMMARY OF THE INVENTION

According to one embodiment, an implantable pulse generator isconfigured to sense cardiac activity and to provide therapeuticelectrical stimulation. The IPG advantageously provides for the downloadof sensed data only when there has been a significant change in the datain order to conserve the battery life of the IPG and minimize dataoverload to the system. The IPG comprises a wireless transceiverconfigured to establish a communications link with an external computingdevice and to broadcast data to and receive data from the externalcomputing device. The IPG further comprises at least one sensorconfigured to sense cardiac activity including the activity of apatient's heart and the performance of the implanted pulse generator. Amemory is configured to store data indicative of the sensed cardiacactivity and further comprises a download schedule including a pluralityof scheduled downloads. A processor of the IPG is configured to analyzethe stored data according to the download schedule in order to determinewhether a significant change has occurred. The processor is furtherconfigured to induce the wireless transceiver to transmit the storeddata to the external computing device when it is determined that asignificant change has occurred. The processor is configured to notundertake one of the plurality of scheduled downloads when it isdetermined that a significant change has not occurred.

According to another embodiment, a cardiac monitoring system is providedincluding an implantable cardiac stimulation device and a monitoringdevice. The implantable cardiac stimulation device has a memory and acommunications link. The implantable cardiac stimulation device providestherapy to the patient's heart in accordance with a plurality ofprogrammed parameters, senses the performance of the device and thepatient's heart, and stores signals indicative thereof in the memory.The implantable cardiac stimulation device categorizes the signals basedupon pre-selected criteria. The monitoring device includes a firstcommunications link that is capable of communicating with theimplantable cardiac stimulation device. The monitoring deviceperiodically queries the implantable cardiac stimulation device forupdate information about the performance of the implantable cardiacstimulation device or the patient's heart. The implantable cardiacstimulation device is configured to transmit update informationgenerated from the stored signals in response to receiving the periodicquery from the monitoring device only when the implantable cardiacstimulation device has categorized the signals based upon thepre-selected criteria as being important enough to warrant transmission.

According to yet another embodiment, a method of controlling a computingdevice that is configured to communicate with an implantable device inorder to read a first set of data from the implantable device isprovided. The method allows for the immediate download of data relatingto an emergency event detected by the implantable device and for thegeneration of an alarm signaling the emergency event. The methodcomprises the computing device establishing a wireless communicationslink with the implantable device and reading an indicator in theimplantable device. The computing device downloads the first set of datawhen the indicator indicates that a first event has occurred. Thecomputing device then resets the indicator in the implantable device sothat it indicates that that the first set of data has been downloaded.The method further comprises generating an alarm when the indicatorindicates that the first event has occurred.

Accordingly, different embodiments allow for the efficient control andmonitoring of an IPG or an implantable cardiac stimulation device sothat a data download is attempted to an RMU as soon as the IPG is inproximity of an RMU after an emergency event has occurred. Downloadsotherwise occur in some embodiments according to a schedule, butscheduled downloads may be canceled if it is determined that the datastored in the IPG has not changed significantly. In some embodiments,alarms are generated by the RMU to notify those nearby or medicalprofessionals at remote locations in order to provide assistance when anemergency event occurs.

Throughout the disclosure, reference is made to an IPG in order todescribe certain aspects of the invention. However, a skilled artisanwill understand that some or all of the features described herein may beapplied to other implantable devices. Specifically, other implantabledevices that are capable of detecting physiologic events and/ormonitoring their own behavior, and that are capable of transferring suchdata to a programmer in a medical facility or to an RMU outside of amedical facility, may be used according to certain embodiments of theinvention. Accordingly, the disclosure provided here may apply not onlyto sensed data indicative of the activity of the heart, but to anysensed data indicative of a patient's medical condition. Furthermore,the disclosure may apply to devices that monitor activity or deviceperformance without providing any type of therapy, such as electricalstimulation therapy.

For purposes of summarizing the invention, certain aspects, advantages,and novel features of the invention have been described herein. It is tobe understood that not necessarily all such advantages may be achievedin accordance with any particular embodiment of the invention. Thus, theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention may be morereadily understood by reference to the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a simplified diagram illustrating an implantable stimulationdevice in electrical communication with three leads implanted into apatient's heart for delivering multi-chamber stimulation and shocktherapy, according to an embodiment of the invention;

FIG. 2 is a functional block diagram of a multi-chamber implantablestimulation device illustrating the basic elements of a stimulationdevice, which can provide cardioversion, defibrillation, and pacingstimulation in four chambers of the heart, according to an embodiment ofthe invention;

FIG. 3 is a functional block diagram of an external programmer device,according to an embodiment of the invention;

FIG. 4 is a diagram of a system for connecting an implanted cardiacdevice to a computing station at a medical facility, according to anembodiment of the invention;

FIG. 5 is a flow chart describing a method for intelligently controllingthe recording and transfer of data from an implantable pulse generatorbased upon the occurrence of a significant event or change in storeddata, according to one embodiment of the invention;

FIG. 6 is a flow chart describing a method for intelligently controllingthe scheduled download of data to a remote monitoring unit based uponthe occurrence of a significant event or change in stored data,according to an embodiment of the invention;

FIG. 7 is a flow chart describing a method for intelligently controllingthe download of data to a remote monitoring unit based upon theoccurrence of a significant event, according to an embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description is of the best mode presently contemplated forpracticing the invention. This description is not to be taken in alimiting sense but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe ascertained with reference to the issued claims. In the descriptionof the invention that follows, like numerals or reference designatorswill be used to refer to like parts or elements throughout.

According to an embodiment shown in FIG. 1, there is an implanted pulsegenerator throughout IPG 10 in electrical communication with a patient'sheart 12 by way of three leads, 20, 24 and 30, suitable for deliveringmulti-chamber stimulation and shock therapy. To sense atrial cardiacsignals and to provide right atrial chamber stimulation therapy, the IPG10 is coupled to an implantable right atrial lead 20 having an atrialtip electrode 22, which typically is implanted in the patient's rightatrium, often in the atrial appendage but not limited to this position.

To sense left atrial and ventricular cardiac signals and to provide leftchamber pacing therapy, the IPG 10 is coupled to a “coronary sinus” lead24 designed for placement in the “coronary sinus region” via thecoronary sinus is for positioning a distal electrode adjacent to theleft ventricle and/or additional electrode(s) adjacent to the leftatrium. As used herein, the phrase “coronary sinus region” refers to thevenous vasculature of the left ventricle, including any portion of thecoronary sinus, great cardiac vein, left marginal vein, left posteriorventricular vein, middle cardiac vein, and/or small cardiac vein or anyother cardiac vein accessible by the coronary sinus.

Accordingly, an exemplary coronary sinus lead 24 is designed to receiveatrial and ventricular cardiac signals and to deliver left ventricularpacing therapy using a left ventricular tip electrode 26, left atrialpacing therapy using a left atrial ring electrode 27, and shockingtherapy using a left atrial coil electrode 28. For a completedescription of a coronary sinus lead, see U.S. Pat. No. 5,466,254,“Coronary Sinus Lead with Atrial Sensing Capability” (Helland), whichpatent is hereby incorporated herein by reference.

The IPG 10 is also shown in electrical communication with the patient'sheart 12 by way of an implantable right ventricular lead 30 having, inthis embodiment, a right ventricular tip electrode 32, a rightventricular ring electrode 34, a right ventricular (VR) coil electrode36, and an SVC coil electrode 38. Typically, the right ventricular lead30 is transvenously inserted into the heart 12 so as to place the rightventricular tip electrode 32 in the right ventricular apex so that theVR coil electrode 36 will be positioned in the right ventricle and theSVC coil electrode 38 will be positioned in the superior vena cava.Accordingly, the right ventricular lead 30 is capable of receivingcardiac signals, and delivering stimulation in the form of pacing andshock therapy to the right ventricle. The right ventricular tipelectrode 32, however can be placed virtually any place in the rightventricle such as the mid-septal region or the right ventricular outflowtract and is not limited to the right ventricular apex.

While IPG 10 is shown in this embodiment as having certain leads,according to other embodiments IPG 10 may additionally or alternativelycomprise other sensors and leads. For example, IPG 10 may sense theelectrical activity of a patient's heart 12 utilizing a multipleelectrode lead having 8, 16, 32 or some other number of electrodesspatially distributed across at least one chamber of the heart 12. Insome embodiments other sensors may be used such as pressure sensors, orthe like.

According to an embodiment illustrated in FIG. 2, a simplified blockdiagram is shown of the multi-chamber IPG 10, which is capable oftreating both fast and slow arrhythmias with stimulation therapy, suchas cardioversion, defibrillation, and pacing stimulation. While aparticular multi-chamber device is shown, this is for illustrationpurposes only, and one of skill in the art could readily duplicate,eliminate, or disable the appropriate circuitry in any desiredcombination to provide a device capable of treating the appropriatechamber(s) with cardioversion, defibrillation, and pacing stimulation.In certain embodiments of the invention, an implanted device may beutilized having appropriate circuitry for sensing the electricalactivity of the heart without circuitry for providing stimulationtherapy.

The housing 40 for the IPG 10, shown schematically in FIG. 2, is oftenreferred to as the “can”, “case”, or “case electrode” and will act asthe return electrode for all “unipolar” modes. The housing 40 canfurther be used as a return electrode alone or in combination with oneor more of the coil electrodes, 28, 36, and 38, for shocking purposes.The housing 40 further comprises a connector (not shown) having aplurality of terminals, 42, 44, 46, 48, 52, 54, 56, and 58 (shownschematically and, for convenience, the names of the electrodes to whichthey are connected are shown next to the terminals). As such, to achieveright atrial sensing and pacing, the connector comprises a right atrialtip terminal (AR TIP) 42 adapted for connection to the atrial tipelectrode 22.

To achieve left chamber sensing, pacing, and shocking, the connectorcomprises a left ventricular tip terminal (VL TIP) 44, a left atrialring terminal (AL RING) 46, and a left atrial shocking terminal (ALCOIL) 48, which are adapted for connection to the left ventricular tipelectrode 26, the left atrial ring electrode 27, and the left atrialcoil electrode 28, respectively.

To support right chamber sensing, pacing, and shocking, the connectorfurther comprises a right ventricular tip terminal (VR TIP) 52, a rightventricular ring terminal (VR RING) 54, a right ventricular shockingterminal (VR COIL) 56, and an SVC shocking terminal (SVC COIL) 58, whichare adapted for connection to the right ventricular tip electrode 32,right ventricular ring electrode 34, the RV coil electrode 36, and theSVC coil electrode 38, respectively.

At the core of the IPG 10 is a programmable microcontroller 60, whichcontrols the various modes of stimulation therapy. As is well known inthe art, the microcontroller 60 typically comprises a microprocessor, orequivalent control circuitry, designed specifically for controlling thedelivery of stimulation therapy and can further include RAM or ROMmemory, logic and timing circuitry, state machine circuitry, and I/Ocircuitry. Typically, the microcontroller 60 comprises the ability toprocess or monitor input signals (data) as controlled by a program codestored in a designated block of memory. The details of the design andoperation of the microcontroller 60 are not critical to the presentinvention. Rather, any suitable microcontroller 60 can be used thatcarries out the functions described herein. The use ofmicroprocessor-based control circuits for performing timing and dataanalysis functions are well known in the art.

As shown in FIG. 2, an atrial pulse generator 70 and a ventricular pulsegenerator 72 generate pacing stimulation pulses for delivery by theright atrial lead 20, the right ventricular lead 30, and/or the coronarysinus lead 24 via an electrode configuration switch 74. It is understoodthat in order to provide stimulation therapy in each of the fourchambers of the heart, the atrial and ventricular pulse generators, 70and 72, can include dedicated, independent pulse generators, multiplexedpulse generators, or shared pulse generators. The pulse generators, 70and 72, are controlled by the microcontroller 60 via appropriate controlsignals, 76 and 78, respectively, to trigger or inhibit the stimulationpulses.

The microcontroller 60 further comprises timing control circuitry 79that is used to control the timing of such stimulation pulses (e.g.,pacing rate, atrio-ventricular (AV) delay, inter-atrial conduction (A-A)delay, or inter-ventricular conduction (V-V) delay, etc.) as well as tokeep track of the timing of refractory periods, PVARP intervals, noisedetection windows, evoked response windows, alert intervals, markerchannel timing, etc., which is well known in the art.

The switch 74 comprises a plurality of switches for connecting thedesired electrodes to the appropriate I/O circuits, thereby providingelectrode programmability. Accordingly, the switch 74, in response to acontrol signal 80 from the microcontroller 60, determines the polarityof the stimulation pulses (e.g., unipolar, bipolar, combipolar, etc.) byselectively closing the appropriate combination of switches (not shown)as is known in the art.

Atrial sensing circuits 82 and ventricular sensing circuits 84 can alsobe selectively coupled to the right atrial lead 20, coronary sinus lead24, and the right ventricular lead 30, through the switch 74 fordetecting the presence of cardiac activity in each of the four chambersof the heart. Accordingly, the atrial (ATR. SENSE) and ventricular (VTR.SENSE) sensing circuits, 82 and 84, can include dedicated senseamplifiers, multiplexed amplifiers, or shared amplifiers. The switch 74determines the “sensing polarity” of the cardiac signal by selectivelyclosing the appropriate switches, as is also known in the art. In thisway, the clinician can program the sensing polarity independent of thestimulation polarity.

Each sensing circuit, 82 and 84, preferably employs one or more lowpower, precision amplifiers with programmable gain and/or automatic gaincontrol, bandpass filtering, and a threshold detection circuit, as knownin the art, to selectively sense the cardiac signal of interest. Theautomatic gain control enables the IPG 10 to deal effectively with thedifficult problem of sensing the low amplitude signal characteristics ofatrial or ventricular fibrillation. The outputs of the atrial andventricular sensing circuits, 82 and 84, are connected to themicrocontroller 60 which, in turn, are able to trigger or inhibit theatrial and ventricular pulse generators, 70 and 72, respectively, in ademand fashion in response to the absence or presence of cardiacactivity in the appropriate chambers of the heart. The sensing circuits,82 and 84, in turn, receive control signals over signal lines, 86 and88, from the microcontroller 60 for purposes of controlling the gain,threshold, polarization charge removal circuitry (not shown), and thetiming of any blocking circuitry (not shown) coupled to the inputs ofthe sensing circuits, 82 and 86, as is known in the art.

For arrhythmia detection, the IPG 10 utilizes the atrial and ventricularsensing circuits, 82 and 84, to sense cardiac signals to determinewhether a rhythm is physiologic or pathologic. As used herein “sensing”is reserved for the noting of an electrical signal, and “detection” isthe processing of these sensed signals and noting the presence of anarrhythmia. The timing intervals between sensed events (e.g., P-waves,R-waves, and depolarization signals associated with fibrillation, whichare sometimes referred to as “F-waves” or “Fib-waves”) are thenclassified by the microcontroller 60 by comparing them to a predefinedrate zone limit (i.e., bradycardia, normal, low rate VT, high rate VT,and fibrillation rate zones) and various other characteristics (e.g.,sudden onset, stability, physiologic sensors, and morphology, etc.) inorder to determine the type of remedial therapy that is needed (e.g.,bradycardia pacing, anti-tachycardia pacing, cardioversion shocks ordefibrillation shocks, collectively referred to as “tiered therapy”).

Cardiac signals are also applied to the inputs of an analog-to-digital(ND) data acquisition system 90. The data acquisition system 90 isconfigured to acquire intracardiac electrogram (EGM) signals, convertthe raw analog data into a digital signal, and store the digital signalsfor later processing and/or telemetric transmission to an externaldevice 102. The data acquisition system 90 is coupled to the rightatrial lead 20, the coronary sinus lead 24, and the right ventricularlead 30 through the switch 74 to sample cardiac signals across any pairof desired electrodes.

Advantageously, the data acquisition system 90 can be coupled to themicrocontroller, or other detection circuitry, for detecting an evokedresponse from the heart 12 in response to an applied stimulus, therebyaiding in the detection of “capture”. Capture occurs when an electricalstimulus applied to the heart is of sufficient energy to depolarize thecardiac tissue, thereby causing the heart muscle to contract. Themicrocontroller 60 detects a depolarization signal during a windowfollowing a stimulation pulse, the presence of which indicates thatcapture has occurred. The microcontroller 60 enables capture detectionby triggering the ventricular pulse generator 72 to generate astimulation pulse, starting a capture detection window using the timingcontrol circuitry 79 within the microcontroller 60, and enabling thedata acquisition system 90 via control signal 92 to sample the cardiacsignal that falls in the capture detection window and, based on theamplitude, determines if capture has occurred.

Capture detection can occur on a beat-by-beat basis or on a sampledbasis. Preferably, a capture threshold search is performed once a dayduring at least the acute phase (e.g., the first 30 days) and lessfrequently thereafter. A capture threshold search would begin at adesired starting point (either a high energy level or the level at whichcapture is currently occurring) and decrease the energy level untilcapture is lost. The lowest value at which there is consistent captureis known as the capture threshold. Thereafter, a safety margin or aworking margin is added to the capture threshold.

The microcontroller 60 is further coupled to a memory 94 by a suitabledata/address bus 96, wherein the programmable operating parameters usedby the microcontroller 60 are stored and modified, as required, in orderto customize the operation of the IPG 10 to suit the needs of aparticular patient. Such operating parameters define, for example,pacing pulse amplitude, pulse duration, electrode polarity, rate,sensitivity, automatic features, arrhythmia detection criteria, and theamplitude, waveshape, and vector of each shocking pulse to be deliveredto the patient's heart 12 within each respective tier of therapy. Anembodiment of the invention senses and stores a relatively large amountof data (e.g., from the data acquisition system 90), which data can thenbe used for subsequent analysis to guide the programming of the IPG 10.

Advantageously, the operating parameters of the IPG 10 can benon-invasively programmed into the memory 94 through a telemetry circuit100 in telemetric communication with the external device 102, such as aremote monitoring unit, programmer, transtelephonic transceiver, or adiagnostic system analyzer. The telemetry circuit 100 is activated bythe microcontroller by a control signal 106. The telemetry circuit 100advantageously allows intracardiac electrograms and status informationrelating to the operation of the IPG 10 (as contained in themicrocontroller 60 or memory 94) to be sent to the external device 102through an established communication link 104.

In the preferred embodiment, the IPG 10 further comprises a physiologicsensor 108, commonly referred to as a “rate-responsive” sensor becauseit is typically used to adjust pacing stimulation rate according to theexercise state of the patient. However, the physiological sensor 108 canfurther be used to detect changes in cardiac output, changes in thephysiological condition of the heart, or diurnal changes in activity(e.g., detecting sleep and wake states). Accordingly, themicrocontroller 60 responds by adjusting the various pacing parameters(such as rate, AV Delay, V-V Delay, etc.) at which the atrial andventricular pulse generators, 70 and 72, generate stimulation pulses.While shown as being included within the IPG 10, it is to be understoodthat the physiologic sensor 108 can also be external to the IPG 10, yetstill be implanted within or carried by the patient. A common type ofrate responsive sensor is an activity sensor, such as an accelerometeror a piezoelectric crystal, which is mounted within the housing 40 ofthe IPG 10. Other types of physiologic sensors are also known, forexample, sensors that sense the oxygen content of blood, respirationrate and/or minute ventilation, pH of blood, ventricular gradient, etc.However, any sensor can be used that is capable of sensing aphysiological parameter that corresponds to the exercise state of thepatient. The type of sensor used is not critical and is shown only forcompleteness.

The stimulation device additionally comprises a battery 110, whichprovides operating power to the circuits shown in FIG. 2, includingtelemetry circuit 100. For the IPG 10, which employs shocking therapy,the battery 110 is capable of operating at low current drains for longperiods of time, and then be capable of providing high-current pulses(for capacitor charging) when the patient requires a shock pulse. Thebattery 110 also has a predictable discharge characteristic so thatelective replacement time can be detected. Accordingly, the IPG 10preferably employs lithium/silver vanadium oxide batteries.

The IPG 10 further comprises magnet detection circuitry (not shown),coupled to the microcontroller 60. It is the purpose of the magnetdetection circuitry to detect when a magnet is placed over the IPG 10,which magnet can be used by a clinician to perform various testfunctions of the IPG 10 and/or to signal the microcontroller 60 that theexternal programmer 102 is in place to receive or transmit data to themicrocontroller 60 through the telemetry circuits 100. However, themagnet detection circuitry is not necessary to establish a communicationlink 104 according to some embodiments. In certain embodiments, themagnetic detection circuitry may trigger specific behavior such assignaling the status of the battery 110 or storing an electrogram.

As further shown in FIG. 2, the IPG 10 is shown as having an impedancemeasuring circuit 112, which is enabled by the microcontroller 60 via acontrol signal 114. The known uses for an impedance measuring circuit112 include, but are not limited to, lead impedance surveillance duringthe acute and chronic phases for proper lead positioning ordislodgement; detecting operable electrodes and automatically switchingto an operable pair if dislodgement occurs; measuring respiration orminute ventilation; measuring thoracic impedance for determining shockthresholds; detecting when the device has been implanted; measuringstroke volume; and detecting the opening of heart valves, etc. Theimpedance measuring circuit 112 is advantageously coupled to the switch74 so that any desired electrode can be used.

In the case where the IPG 10 is intended to operate as an implantablecardioverter/defibrillator (ICD) device, it detects the occurrence of anarrhythmia, and automatically applies an appropriate electrical shocktherapy to the heart aimed at terminating the detected arrhythmia. Tothis end, the microcontroller 60 further controls a shocking circuit 116by way of a control signal 118. The shocking circuit 116 generatesshocking pulses of low (up to 0.5 Joules), moderate (0.5-10 Joules), orhigh energy (11 to 40 Joules), as controlled by the microcontroller 60.Such shocking pulses are applied to the patient's heart 12 through atleast one shocking electrode but potentially more shocking electrodes,and as shown in this embodiment, selected from the left atrial coilelectrode 28, the RV coil electrode 36, and/or the SVC coil electrode38. As noted above, the housing 40 can act as an active electrode incombination with the RV electrode 36, or as part of a split electricalvector using the SVC coil electrode 38 or the left atrial coil electrode28 (i.e., using the RV electrode as a common electrode).

Cardioversion shocks are generally considered to be of low to moderateenergy level (so as to conserve battery life), and/or synchronized withan R-wave and/or pertaining to the treatment of tachycardia.Defibrillation shocks are generally of moderate to high energy level(i.e., corresponding to thresholds in the range of 5-40 Joules), andpertaining to the treatment of fibrillation. Accordingly, themicrocontroller 60 is capable of controlling the synchronous orasynchronous delivery of the shocking pulses.

Microcontroller 60 of the IPG 10 further comprises an event flag module123. As discussed below, flag 123 can be set by an external device 102in order to indicate that the external device 102 has downloaded datacontained in the memory 94 of microcontroller 60. When the externaldevice 102 sets the flag 123, the flag 123 may correspond to an enabledcondition and in some embodiments a logical “I” value. Themicrocontroller 60 is further configured in some embodiments to set theflag 123 when an event has occurred to a disabled condition,corresponding in some embodiments to a logical “0” value. The use of aparticular electrical value or signal for each condition of the flagmay, of course, be varied depending on a particular design choice. Insome embodiments, flag 123 includes multiple flags corresponding to avariety of indicators for indicating different events or conditions. Aswill be explained in more detail below, the flag 123 may therefore beused in some embodiments to indicate when a remote monitoring unit 62should download data from the IPG 10.

FIG. 3 is a functional block diagram of one embodiment of the externaldevice 102, such as a physician's programmer or remote monitoring unit.The external device 102 comprises a CPU 122 in communication with aninternal bus 124. The internal bus 124 provides a common communicationlink and power supply between various electrical components of theexternal device 102, such as the CPU 122. The external device 102 alsocomprises memory and data storage such as ROM 126, RAM 130, and a harddrive 132 commonly in communication with the internal bus 124. The ROM126, RAM 130, and hard drive 132 provide temporary memory andnon-volatile storage of data in a well known manner. In one embodiment,the ROM 126, RAM 130, and hard drive 132 can store control programs andcommands for upload to the IPG 10 as well as operating software fordisplay of data received from the IPG 10. It will be appreciated that incertain embodiments alternative data storage/memory devices, such asflash memory, can be included or replace one or more of the ROM 126, RAM130, and hard drive 132 without detracting from the spirit of theinvention.

The external device 102 also comprises a display 134. The display 134 isadapted to visually present graphical and alphanumeric data in a mannerwell understood in the art. The external device 102 also comprises inputdevices 136 to enable a user to provide commands and input data to theexternal device 102. In one embodiment, the input devices 136 include akeyboard 140, a plurality of custom keys 142, and a touch screen 144aspect of the display 134. The keyboard 140 facilitates entry ofalphanumeric data into the external device 102. The custom keys 142 areprogrammable to provide one touch functionality of predefined functionsand/or operations. The custom keys 142 can be embodied as dedicatedtouch keys, such as associated with the keyboard 140 and/or predefinedareas of the touch screen 144. In this embodiment, the external device102 also comprises a speaker 146 and a printer 150 in communication withthe internal bus 124. The speaker 146 is adapted to provide audiblealert send signals to a user. The printer 150 is adapted to provide aprinted readout of information from the external device 102.

In this embodiment, the external device 102 also comprises a CD drive152 and a floppy drive 154 which together provide removable datastorage. In this embodiment, the external device also comprises aparallel input-output (IO) circuit 156, a serial IO circuit 160, and ananalog output circuit 162. In certain embodiments, the external device102 also comprises a USB interface. In some embodiments, the externaldevice 102 may also comprise an industry standard interface compatiblewith other portable storage devices such as a flash memory device. Thesecircuits 156, 160, 162 provide a variety of communication capabilitiesbetween the external device 102 and other devices in a manner wellunderstood in the art.

The external device 102 also comprises an electrocardiogram (ECG)circuit 170 in communication with a plurality of ECG leads 172. The ECGcircuit 170 and the ECG leads 172 obtain electrical signals from thesurface of a patient's body and configure the signals for display as anECG waveform on the display 134 of the external device 102.

The external device 102 also comprises a telemetry CPU 164 and atelemetry circuit 166, which establish the telemetric link 104 incooperation with the IPG 10. The telemetric link 104 comprises abidirectional link to enable the external device 102 and the IPG 10 toexchange data and/or commands. As previously noted, the establishment ofthe telemetric link 104 is in certain embodiments facilitated by a wandor programmer head, which is placed in proximity to the IPG 10. The wandor programmer head facilitates establishment of the telemetric link 104by placing an antenna structure in a closer proximity to the IPG 10 tofacilitate conduction of transmitted signals to the external device 102.

The telemetric link 104 can in some embodiments comprise a variety ofcommunication protocols appropriate to the needs and limitations of agiven application. In certain embodiments, the telemetric link 104comprises radio frequency (RF) telemetry. In one particular embodiment,the telemetric link 104 comprises a frequency modulated digitalcommunication scheme wherein logic ones are transmitted at a firstfrequency A and logic zeros are transmitted second frequency B. As theIPG 10 is powered by a battery having limited capacity and in certainembodiments the external device 102 is powered by line voltage, e.g.,not subject to the stringent power limitations of the IPG 10, thebidirectional telemetric link 104 can proceed in an asymmetric manner.For example, in one embodiment, a transmission power and data rate fromthe external device 102 to the IPG 10 via the telemetric link 104 canproceed at higher power levels and/or higher data transmission ratesthan the reciprocal data rates and transmission power from the IPG 10 tothe external device 102. The telemetry circuit 100 of the IPG 10 as wellas the telemetry circuit 166 and CPU 164 of the external device 102 canselect or be adjusted to provide a desired communication protocol andtransmission power.

FIG. 4 shows an example of a remote monitoring system comprising a homelocation 405 and a medical facility 445 connected over a network 450.The home location includes a patient 400 with an implanted pulsegenerator 10 which in this implementation is an implanted cardiacstimulation device. IPG 10 collects data indicative of the activity ofthe heart of patient 400, as described above with reference to FIGS. 1and 2. Home location 405 further includes a remote monitoring unit 410.RMU 410 may be an external device 102 as described above with referenceto FIG. 3, but may be specifically adapted for use in a home, office, orother location outside a typical medical setting. RMU 410 periodicallycommunicates with the IPG 10 implanted in the patient 400 in order toupload cardiac data collected by the IPG 10.

Data collected by the IPG 10 and transferred to the RMU 410 may betransferred over a network 450. In some embodiments, network 450corresponds to the Internet. In other embodiments, network 450 comprisesa local area network. For example, network 450 may comprise a local areanetwork in a hospital or other medical facility. In still otherembodiments, network 450 corresponds to a direct connection betweencomputing devices, a wireless network, or the like.

Data transferred over the network 450 may further be stored on a server420. Server 420 may comprise any computing device capable ofcommunicating over network 420, such as a personal computer or bladeserver. In some embodiments, server 420 may store and operate a hospitalor medical database system that contains patient data and records. Theserver may include software that allows access to the database system bycertain medical professionals 440 and by the RMU 410.

A monitoring station 430 located at medical facility 445 accesses thedata stored on server 420 over the network 450. In some otherembodiments, monitoring station 430 may download patient data directlyfrom the RMU 410. Monitoring station 430 obtains the patient data storedon server 420 and displays the data to a physician or clinician 440. Aphysician or clinician 440 may use monitoring station 430 in order toview some or all the patient data according to the display software ofthe monitoring station 430. Monitoring station 430 may have some or allof the same functionality of the external device 102 shown in FIG. 3.For example, monitoring station 430 may not include a telemetry circuit166 in some embodiments. In some embodiments, monitoring station 430further comprises other features, such as an alarm or ethernet port.

While the system shown in FIG. 4 conveniently allows for the transfer ofinformation from an IPG 10 to a medical provider without requiring thepatient 400 to travel to the medical facility 445, the transfer ofinformation from implanted IPG 10 to RMU 410 requires more powerconsumption than the standard operation of implanted IPG 10 because thetransmitter must be powered. As more data is transferred from implantedIPG 10, and at a higher frequency, the amount of power required by thisprocess increases. As that occurs, the useful life of the implanted IPG10 decreases. When the batteries are near or at their depleted levelsthe user must have them replaced, which may involve invasive surgery.Thus, it is desired that the battery life of the IPG 10 be extended asmuch as possible.

However, the less frequent download of data sensed by the implanted IPG10 increases the likelihood that a major event, such as a patientmedical condition or a device failure, will not be detected by theremote monitoring unit 410 and the relevant information sent toclinician or physician 440 until it is too late to provide patient 400with the necessary treatment. Current systems may have this problem,because they operate on periodic cycles of set times. Thus, whether datais downloaded once per week, once per day, or once per hour, there is asignificant amount of time between downloads. If a patient 400experiences a medical emergency or there is a device failure shortlyafter a download occurs, then the next scheduled download will not occurfor a relatively long time. If the patient 400 is not aware of thisevent or is unable to contact a physician 440 or other emergency medicaltechnician for assistance, the necessary medical attention may not bereceived.

According to some embodiments, these problems related to battery lifeand critical events are substantially reduced. For example, according tosome embodiments, the battery life of an IPG 10 may be extended by onlydownloading information that reflects a significant change, or onlydownloading information related to the occurrence of an event. When thetime period for the scheduled download occurs and there is notsignificant information to download, the download can be limited so asto minimize unnecessary battery depletion.

Alternatively, in order to provide efficient and fast assistance duringa significant event, a system is provided for causing the IPG 10 totransfer information to the RMU 410 after the occurrence of an event andas soon as the implanted IPG 10 is in range of the RMU 410 rather thanwaiting for a download period. Thus, as will be described in more detailbelow, the more efficient and intelligent monitoring of data collectedby an IPG 10 is achieved according to some embodiments of the currentinvention.

FIG. 5 is a flow chart describing a process 500 for the efficientcollection and analysis of data sensed by an IPG 10 according to oneembodiment. The process 500 may be utilized, for example, by an IPG 10when sensing data indicative of the activity of a patient's heart 12 andcommunicating with an RMU 410.

The process 500 begins at state 501 where the IPG 10 monitors heart anddevice activity. For example, the IPG 10 may monitor the electricalactivity of the patient's heart 12 as sensed by VL tip electrode 26, theVR tip electrode 32, or AR tip electrode 22. IPG 10 may further sensedata such as pressure data, movement data, impedance measurements,battery life, or the like. Based on the monitored heart and deviceactivity, the IPG 10 may determine the occurrence of an event. An eventmay include a medical event, such as an arrhythmia, or the like. Anevent may also include a device event such a dislodged or damaged leador a low battery.

The process 500 continues to decision state 502. At decision state 502the IPG 10 determines if a recordable event has been detected. In someembodiments, parameters determining what constitutes a recordable eventare programmed, for example, by a physician using an external programmer102. In some embodiments, any event detected by IPG 10 is recordable. Inother embodiments only a limited number of events are recorded topreserve limited memory space. If it is determined that its decisionstate 502 that a recordable event has occurred, then the process 500proceeds to state 503. Otherwise the process 500 continues to state 509.

At 503, the detected event is recorded and stored in the memory 94 ofthe IPG 10. In some embodiments, data collected by the IPG 10 is storedin the memory 94 for predetermined amount of time before being erased.In such embodiments, when it is determined at decision state 502 arecordable event has occurred, then the IPG 10 may prevent datarepresenting that event from being erased from memory 94. In someembodiments, certain events may be detected at their outset and recordedand stored in memory 94 only after they have been detected. In someembodiments, only an indicator that an event has occurred is stored,rather than the data surrounding the event. For example, a low batteryevent might cause an indication of the low battery to be stored ratherthan measured data. Similarly, the incident of a capture threshold maybe recorded rather than measured amplitude.

The process 500 then continues to decision state 504. At decision state504 it is determined whether the recorded event constitutes a high riskor emergency event. A high risk or emergency event may be determined bythe IPG 10 based on predetermined factors. In some embodiments, thesefactors are programmed using an external programmer 102 by a physician.High risk or emergency events may represent, for example, a medicalcondition that requires immediate medical attention in order to preventpatient injury or death such as the occurrence of a new type of heartarrhythmia or the occurrence of particularly severe or frequent heartarrhythmias. A high risk event may also correspond to a devicemalfunction or condition requiring immediate medical attention, such asa very low battery life or a broken or dislodged lead. If it isdetermined at decision state 504 that the recorded event is not a highrisk or emergency event, then the process 500 continues to state 509. Ifit is determined at decision state 504 that the recorded eventconstitutes a high risk or emergency event, then the process 500continues to state 505.

At state 505, the IPG 10 disables the flag of the event flag module 123.Although in the description of process 500 only one flag is utilized, itis understood that in other embodiments multiple flags may be used byIPG 10. For example, certain flags may indicate different types ofconditions. For example, one flag may indicate a device malfunction andanother flag may indicate a medical condition. In some embodiments, anumber of flags may be used and may be programmed by a physician usingan external programmer 102. The flag disabled at state 505 signifiesthat at least one type of high risk or emergency event has occurredsince the last data download by the RMU 410.

The process 500 then continues to decision state 506. At decision state506, it is determined whether the IPG 10 is connected to RMU 410 over awireless communications link 104. If the IPG 10 is in range of the RMU410 and is connected, then the process 500 proceeds to state 508. If theRMU 410 is not connected to the IPG 10, then the process 500 continuesto state 507. At state 507 of the process 500, the IPG 10 waits andattempts to connect with the RMU 410. For example, the IPG 10 may waituntil the RMU 410 is within range. For example, a patient having an IPG10 may have an RM 410 located in his or her home. If the patient is awayfrom the home when an event is detected, then the IPG 10 will connectwith the RMU 410 when the patient returns home and is within range ofthe RMU 410 such that the IPG senses the proximity of the RMU, e.g. byreceiving a polling signal from the RMU 410. In some embodiments, theIPG 10 continues to record data related to the current activity of thepatient's heart 12 or the IPG 10. The process 500 then continues tostate 508. At state 508, the IPG 10 which is connected to the RMU 410transmits the notification of the high risk or emergency eventdetermined at decision state 504 to the RMU 410.

The IPG 10 then proceeds to perform a full download of the data storedin the memory 94 of the IPG 10 to the RMU 410. In some embodiments, allof the data stored in the memory 94 is downloaded by the RMU 410 duringa full download. In other embodiments, only data related to the changeddata or a significant event is downloaded. In some embodiments, the datato be downloaded is determined based on one or more indicators or flags123. Process 500 continues from state 513 to state 514 where the flag ofthe event flag module 123 is reset. The set flag indicates in someembodiments that a full data download has occurred, and that no majorevents have occurred since that time.

Returning to decision state 502, if no recordable event is detected,then the process 500 continues to decision state 509. At decision state509 it is determined whether or not a scheduled download should occur. Ascheduled download may be determined by the IPG 10 or by the RMU 10. Insome embodiments, an external programmer 102 is used by a physician toprogram a download schedule into the memory 94 of the IPG 10. In someembodiments, a download schedule is maintained by the RMU 410 and theIPG 10 determines at decision state 509 whether a scheduled downloadshould occur based upon whether or not a query has been received fromthe RMU 410. If no scheduled download should occur, then the process 500returns to state 501 and continues sensing monitored heart and deviceactivity. Of course, in some embodiments, the IPG 10 continues tomonitor heart and device activity throughout the process 500 for all thesteps recited herein. If a download is determined to be scheduled atdecision state 509, then the process 500 continues to decision state510.

At decision state 510 it is determined whether or not a significantchange in stored data has occurred. The IPG 10 may determine whethersignificant change in data has occurred by analyzing data stored inmemory 94 of the IPG 10. The data stored in memory 94 may be comparedand analyzed, based upon, for example, criteria programmed by aphysician using an external programmer 102. For example, a significantchange in stored data may be determined to have occurred if a certainnumber of events have occurred. In some embodiments, IPG 10 maydetermine whether certain threshold values for a heart rate or othersensed data have been crossed in order to determine whether significantchange in stored data has occurred. If no significant change in storeddata has occurred since the previous download, then the process 500returns to state 501 and the IPG 10 continues to monitor heart anddevice activity. If a significant change in stored data has occurred atdecision state 510, then the process 500 continues to decision state511.

At decision state 511 it is determined whether or not the IPG 10 isconnected to RMU 410. As explained with respect to decision state 506above, this step comprises determining whether or not the RMU 410 is inrange and the communication link 104 has been established. If no suchlink 104 has been established at decision state 511, then the process500 continues to state 512. If a link 104 has been established, then theprocess 500 continues to state 513. At 512, the process 500 waits andattempts to connect the IPG 10 with the RMU 410.

When the IPG 10 is connected with the RMU 410 at state 511 or 512, thenthe process 500 continues to state 513 where a full interrogation ordownload occurs. Sensed data stored in memory 94 of the IPG 10 istransmitted to the RMU 410 as described above. In some embodiments, allof the data stored in memory 94 of the IPG 10 is transmitted to the RMU410. In some embodiments, sensed data is transmitted to the RMU 410 butcertain other data including configuration data and settings are nottransmitted to the RMU 410. In some embodiments, the data transmitted tothe RMU 410 is determined in part based upon whether a high risk eventhas occurred or whether a significant change has occurred, as well asthe specific sensed data corresponding to the events or changes. Forexample, if multiple flags are used with the IPG 10, then the datadownloaded from memory 94 may be determined in part based upon whichflags are disabled.

The process 500 then continues to state 514 where the flag of event flagmodule 123 is reset. The reset flag indicates the data in memory 94 hasbeen downloaded by the RMU 410 since the last event has occurred. Theprocess 500 then returns to state 501 and the IPG 10 continues tomonitor heart and device activity.

While the process 500 describes the operation of the IPG 10 according tosome embodiments, the RMU 410 also may perform some of the steps shownin FIG. 5 and provide additional functionality. FIG. 6 is a flow chartdescribing a process 600 for the efficient monitoring of cardiac datacollected by an IPG 10 according to one embodiment. The process 600 maybe utilized, for example, by an RMU 410 at periodic intervals to collectdata from an implanted IPG 10 when there has been a significant changein the data stored in the memory 94 of the implanted IPG 10, or when anevent has occurred.

The process 600 begins at state 601 when the remote monitoring unit 410recognizes the implanted pulse generator 10 and establishes acommunications link 104. In a preferred embodiment, the RMU 410 attemptsto perform the process 600 at periodic intervals, such as once each dayor once each week. Of course, other periods may be set between attempteddownloads according to the process 600. In the event that the IPG 10 isoutside of the range of the RMU 410 or for some other reason the RMU 410cannot open a communications channel with the IPG 10 at the scheduledtime, then the RMU 410 may continue to attempt to establish contactuntil it is successful. The communications link 104 between the RMU 410and the IPG 10 may comprise any type of wireless transmission, protocolsuch as RF transmissions, as discussed above. At state 601, the IPG 10is in a low power consumption mode, because the IPG 10 is nottransferring significant amounts of data to the RMU 410, but has merelyverified its presence and opened a wireless channel with the RMU 410.

At state 602, the RMU 410 reads the flag 123 in the IPG 10. The flag 123may be in either an enabled or disabled condition. In general, anenabled flag condition corresponds to the flag being set and indicatesthat no event has occurred since the previous data download by the RMU410. A disabled flag condition indicates that between the time that theRMU 410 last downloaded data from the IPG 10, an event has occurred thattriggered the microprocessor 60 of the IPG 10 to disable the flag 123.An event may comprise a medical condition in some embodiments, such as asupraventricular tachycardia, atrial fibrillation, any other arrhythmia,or some other condition that may require medical assistance. In someembodiments, an event may comprise a current or imminent device failure,such as a low battery power level in the IPG, a dislodged lead, or thelike. While this state has been discussed with reference to a singleflag, the IPG 10 may store multiple flags 123 corresponding to differentconditions. For example, the IPG 10 may store one flag 123 related tothe occurrence of a patient medical condition and another flag 123related to the occurrence of an equipment malfunction. In someembodiments, multiple flags correspond to multiple medical conditions,such as one for a high ventricular rate episode, one corresponding to ahigh atrial rate episode, and any others that may be useful indistinguishing events.

At decision state 603, if the flag is set, corresponding to an enabledcondition, then the process 600 continues to state 604. If the flag isnot set, corresponding to a disabled condition, then the process 600continues to state 606.

At state 604, the RMU 410 reads other data stored in the memory 94 ofIPG 10. The other data read at state 604 may comprise a subset of thedata stored in the memory of IPG 10. For example, the subset of data mayindicate whether or not there has been significant change in the largercollection of cardiac data stored by the IPG 10. A significant change inthe data stored by IPG 10 may comprise a change in the average heartrate, the occurrence of electrical stimulation therapy, or the like. Thetransmitting of the subset of data may require more power than onlyreading the flag 123, but may require substantially less power than afull download.

At decision state 605, based on the subset of data read at state 604, itis determined by the RMU 410 whether a significant change has occurredin the larger collection of cardiac data since the last download. Whatconstitutes a significant change may be determined by a physician insome embodiments. If it is determined that a significant change hasoccurred, the process continues to state 606. If a significant changehas not occurred, then the process continues to state 609.

The process 600 reaches state 606 if the flag 123 is not set asdetermined at decision state 603 or there has been significant change inthe data stored in the IPG 10 as determined at decision state 605. Atstate 606, a full interrogation or download of the data stored in thememory 94 of the IPG 10 is performed. During state 606, the IPG maytransfer data collected that is related to, for example, electricalsignals generated by the heart, pulses and other therapeutic stimulationprovided by the IPG 10, impedance measurements sensed by the IPG 10, orthe like. In some embodiments utilizing multiple flags 123, having oneflag 123 that is in a disabled condition may initialize a full download.In some embodiments, having less than all of the flags 123 in a disabledcondition may cause the RMU 410 to download data related to the eventsindicated by any of the flags 123 in a disabled condition, but not todownload data related to the flags 123 in an enabled condition. Adownload at state 606 represents a high power consumption mode for theIPG 10, and therefore some embodiments of the current invention allowfor the efficient use of this process by downloading the full set ofdata only when it is necessary, rather than at every scheduled period.

After data has been downloaded to the RMU 410, the process 600 continuesto state 607. At state 607, the RMU 410 may transmit data collectedduring the download process to server 420. In some embodiments, server420 may store a collection of medical data and may be accessible by amonitoring station 430 located at a medical facility 445 through anetwork 450. In some embodiments, the data downloaded at state 606 andtransmitted to the server 420 at state 607 is read by the server 420 todetermine if the data indicates an event requiring an alarm or othernotification be sent to a physician 440 or any other emergencytechnician at the medical facility 445. If it is determined that acondition exists warranting an alarm be sent, then alarm data istransferred to the monitoring station 430 and is displayed to aphysician or clinician 440 at that location. The alarm data may inducethe monitoring station to sound an audio alarm, display a visual alarmor message, or the like. In some embodiments, an alarm may comprise ane-mail, SMS text message, voice message sent electronically or over anautomated telephone system, pager, fax, or the like. In someembodiments, the server 420 may continue to send an alarm until anacknowledgement is received such as by return e-mail or SMS textmessage.

In some embodiments, an alarm may be provided on the RMU 410 itself.This may be beneficial, for example, where a patient 400 is living witha care provider. In this case, the alarm, whether it is an audio alarmor visual alarm, may alert a care provider to the patient's conditionand possible need for assistance. In some embodiments, an error codedetermined by analyzing the data downloaded from the IPG 10 is used todetermine a specific alarm output by the RMU 410. In some embodiments,this error code may be transmitted with the data at state 607.

The process 600 continues at state 608, where the flag 123 in the IPG 10is set by the RMU 410. The flag 123 indicates that the data contained inthe IPG 10 has been downloaded. With the flag in an enabled condition,as set at state 608, the RMU 410 will not download data from the IPG 10until the next scheduled download period, and then only if significantchange in the data has occurred. State 608 is shown occurring afterstate 607. However, in some embodiments, state 608 may occursubstantially simultaneously with state 607 or before state 607. Oncethe data has been transmitted to the RMU 410 at state 606, and the flaghas been set at state 608, then the IPG 10 returns to a low power statebecause it is no longer transferring the collected data. The process 600then continues to state 609.

At state 609, the RMU 410 continues to maintain a communications link104 with the IPG 10. This link 104 may be maintained as long as the IPG10 is within the wireless communications range of the RMU 410. In someembodiments, this communications channel is only maintained as long as apredetermined percentage of data transfer attempts are successful inorder to avoid the need to use battery life retransmitting previouslysent data that was lost during transmission. When the IPG 10 is inrange, maintaining the handshake with the IPG requires only a low powerconsumption and allows the RMU 410 to maintain efficient contact withthe IPG 10.

The process 600 next continues to decision state 610. At decision state610, it is determined whether the established communication link 104between the RMU 410 and the IPG 10 has been broken. If it is determinedthat the link 104 has not been broken, then the process 600 returns tostate 602 and reads the flag 123 of the IPG 10 at the next scheduleddownload. If it is determined that the communications link between theRMU and the IPG 10 has been broken at state 610, then the RMU waits toreestablish the communication link 104 with the IPG at state 611. Whenit is determined at state 611 that the communications link 104 with theIPG can be reestablished, then the process returns to state 601.

The process 600 described above therefore allows for the efficientperiodic download of data stored on IPG 10 to a remote monitoring unit410. Downloads occur at a periodic interval, but only on the conditionthat a flag has been disabled indicating that an event has occurred, orif there has been a significant change in the stored data. Thus, dataindicating the continued normal operation of the IPG 10 is notdownloaded. This allows the IPG 10 to transmit data stored in memory 94only when necessary. This, in turn, preserves the battery life of theIPG 10 because power is not wasted broadcasting unnecessary information.

FIG. 7 shows an embodiment of a process 700 for downloading informationstored in the IPG 10 when an event occurs between the scheduled downloadtimes. The process 700 advantageously allows for the nearly immediatedownload of data after an event has occurred if the IPG 10 is in rangeof the RMU 410.

The process 700 begins at state 701, where the RMU 410 recognizes theIPG 10 and establishes a communications link 104. The link 104 may beestablished, for example, when the patient enters an area within thebroadcasting range of the RMU 410. For example, this range maycorrespond approximately with the patient's home. In some embodiments,multiple RMUs 410 may be located at different locations including ahome, office, coffee shop, or the like. After a link has beenestablished in state 701, the process continues to state 702.

At state 702, the RMU 410 reads flag 123 of the IPG 10. As discussed inmore detail above with respect to process 600, in some embodimentsmultiple flags 123 may be stored in the IPG 10 and read by RMU 410. Whenmultiple flags 123 are used, any or some combination of the flags 123being disabled may trigger a complete download. In some embodiments,each of the multiple flags 123 may correspond to a type of event anddetermine whether data stored by IPG 10 related to that event isdownloaded. If it is determined at state 703 that the flag 123 is setcorresponding to an enabled condition, then the process continues tostate 709 without performing any download of data. If it is determinedat state 703 that the flag 123 is not set, corresponding to a disabledcondition, then the process 700 continues to state 706 and a fullinterrogation or download is performed. At state 706, the sensed dataindicative of cardiac activity or device performance or condition andstored in the memory 94 of the IPG 10 is transferred from the IPG 10 tothe RMU 410.

At state 707, the RMU 410 transmits the data collected from the IPG 10to server 420. Server 420 may determine that an alarm should be sent tomedical facility 445 indicating that an event has occurred, such as apatient medical condition or a device malfunction. An alarm may beprovided on monitoring station 430 to indicate to a physician 440 orother emergency medical technician that patient 400 may need assistance.An alarm may additionally be provided on RMU 410 indicating an event insome embodiments. As discussed in more detail above, an alarm may beprovided at the medical facility 445, the RMU 410, or be sent by someother method to a physician 440.

At state 708, the flag 123 is set in the IPG 10. The set flag indicatesthat the data stored in the IPG 10 has been downloaded by the RMU 410.Thus, when an event occurs, the flag 123, having been disabled by theIPG 10, will indicate to the RMU 410 that a download is necessary. Atstate 708, after a download has occurred and the information related tothe event has been obtained by the RMU 410, then the flag 123 will againbe set indicating that no further download is necessary at that time. Inthis way, the amount of energy used to transmit information from the IPG10 to the RMU 410 is reduced while allowing for a quick emergencyresponse. In this embodiment, only the information that needs to betransferred is transferred, but that information is transferred as soonas it is needed.

If the flag is set at state 703, or after the flag is set by the RMU 410at state 708, the process 700 continues to state 709. At state 709, theRMU 410 continues the communications link 104 and handshake protocolestablished at state 701 with the IPG 10.

At decision state 710, if it is determined that the link 104 has notbeen broken, then the process 700 returns to state 702 and reads theflag. In some embodiments, this may entail a short wait that is notlikely to endanger the patient 400. For example, the RMU 410 may waitfive minutes, one minute, or less than a minute between attempts to readthe flag 123. This process 700 may occur in some embodiments as long asthe IPG 10 is within range of the transmitter of the RMU 410. If it isdetermined at state 710 that the link 104 has been broken, then theprocess continues to state 711 where the RMU waits to reestablish thecommunications link with the IPG 10. When the IPG 10 is again detected,the process 700 returns to state 701 and establishes the link 104. Thus,according to this embodiment, whenever the RMU 410 is in range of theIPG 10, a communications link 104 is established. If an event occurswhile a communications link 104 is established, such as a medicalemergency or a device failure, then the IPG 10 disables a flagcondition, causing the RMU 410 to determine that data should bedownloaded from the IPG 10.

As can be seen, various embodiments described herein provide a number ofadvantages over the prior art. For example, according to someembodiments of the invention, a remote monitoring unit mayadvantageously monitor data stored in an implanted device over periodicintervals, but only perform a full download when the data has changedsignificantly. This may allow for the more efficient use of theimplanted device battery and longer device life span. According to someembodiments of the invention, a remote monitoring unit may continuallybe in contact and in communication with an IPG whenever the IPG iswithin range of the RMU. Advantageously, the IPG may operate in a lowpower state during this communication while it is not downloading ortransferring any information from the device memory to the RMU. Onlywhen an event occurs and the IPG sets a flag will a data download beinitiated. Thus, the system advantageously allows for the nearlyimmediate download of data related to the occurrence of a significantevent, such as a medical emergency or device failure. It will beunderstood that not all of the advantages described herein may beachieved in each embodiment of the invention. Furthermore, advantagesnot specifically discussed may nonetheless be achieved by someembodiments as taught herein. Nonetheless, those embodiments may bepracticed without departing from the spirit of the invention. An artisanof ordinary skill will also understand that while reference is made tothe monitoring of cardiac activity by an IPG, other implantable devicesthat sense other aspects of a patient's medical condition and transmitsensed data to a monitoring computer may be utilized in order toaccomplish certain advantages described herein without departing fromthe scope of the invention. For example, certain aspects disclosedherein may be utilized with implantable glucose monitors, or the like.

The methods and steps described herein describe particular embodiments,and are not limiting. An artisan of ordinary skill will understand thatcertain steps described herein may be removed or performed in adifferent order, and other steps not described may be added.Furthermore, the steps are generally described as being performed by aremote monitoring unit, but certain steps may be implemented utilizingeither hardware components or software instructions in any computingdevice.

1. An implantable device comprising: a wireless transceiver configuredto establish a communications link with an external computing device andto broadcast data to and receive data from the external computingdevice; at least one sensor that senses activity including the activityof a patient's heart and the performance of the implantable device; amemory that stores data indicative of the sensed activity, the memoryfurther comprising a download schedule including a plurality ofscheduled downloads; and a processor that analyzes the stored dataaccording to the download schedule in order to determine whether asignificant change has occurred, and that induces the wirelesstransceiver to transmit the stored data to the external computing devicewhen it is determined that a significant change has occurred and toinhibit one of the plurality of scheduled downloads when it isdetermined that a significant change has not occurred.
 2. Theimplantable device of claim 1, wherein the at least one sensor comprisesa plurality of sensors that sense at least a first and second type ofdata, and wherein the processor induces the transmission of only thefirst type of data when the processor determines that a significantchange has occurred only in the first type of data and induces thetransmission of only the second type of data when the processordetermines that a significant change has occurred only in the secondtype of data.
 3. The implantable device of claim 1, wherein theprocessor further determines whether an emergency event has occurredbased upon the sensed activity and induces the wireless transceiver totransmit the stored data to the external computing device withoutwaiting for the next scheduled download when it is determined that anemergency event has occurred.
 4. The implantable device of claim 3,wherein the processor further induces the external computing device togenerate an alarm when it is determined that an emergency event hasoccurred.
 5. The implantable device of claim 1, wherein the processordetermines whether a significant change has occurred based on aplurality of pre-selected criteria, and wherein the memory is configuredto store data indicative of the pre-selected criteria provided by anexternal programmer.
 6. The implantable device of claim 5, wherein thepre-selected criteria correspond to at least one of a number of detectedevents, a threshold heart rate, a detected heart arrhythmia, an expectedbattery lifespan, and an expected device performance criteria.
 7. Acardiac monitoring system comprising: an implantable cardiac devicehaving a memory and a communications link, wherein the implantablecardiac device senses the performance of the device and the patient'sheart, stores signals indicative thereof in the memory, and categorizesthe signals based upon a pre-selected criteria; and a monitoring devicethat includes a first communications link capable of communicating withthe implantable cardiac device, wherein the monitoring deviceperiodically queries the implantable cardiac device for updateinformation about the performance of the implantable cardiac device orthe patient's heart; wherein the implantable cardiac device isconfigured to transmit update information generated from the storedsignals in response to receiving the periodic query from the monitoringdevice only when the implantable cardiac device has categorized thesignals based upon the pre-selected criteria as being important enoughto warrant transmission.
 8. The system of claim 7, wherein theimplantable cardiac device further categorizes certain information aboutthe implantable cardiac device or the patient heart as requiringimmediate transmission to the monitoring device upon detection of thepresence of the monitoring device.
 9. The system of claim 7, wherein thepre-selected criteria comprise at least one of a heart rate threshold, adetected arrhythmia, an impedance measurement indicating a dislodgedlead, a data storage error rate, a remaining battery lifespan, and aremaining device lifespan.
 10. The system of claim 7, wherein theimplantable cardiac device is configured to indicate that the signalsare important enough to warrant transmission using at least one dataflag.
 11. The system of claim 10, wherein the at least one data flagcomprises a plurality of data flags wherein each data flag correspondsto different types of data, and wherein the implantable cardiac deviceis configured to transmit update information related to only the typesof data corresponding to ones of the plurality of data flags thatindicate the type of data is important enough to warrant transmission.12. A method for controlling the download of information sensed by animplantable cardiac device, comprising the steps of: sensing cardiacactivity; monitoring the performance of the implantable cardiac device;determining whether an event has occurred based on collected datacorresponding to the sensed cardiac activity and to the performance ofthe implantable cardiac device; storing the collected data indicative ofthe event when the event has occurred; determining whether the eventcorresponds to a dangerous condition when the event has occurred;setting an indicator that induces an immediate data download to anexternal monitoring device when it is determined that the eventcorresponds to a dangerous condition; and resetting the indicator afterthe data download.
 13. The method of claim 12, wherein determiningwhether the event has occurred comprises analyzing the collected databased on a plurality of pre-selected criteria.
 14. The method of claim12, wherein determining whether the event corresponds to a dangerouscondition comprises analyzing the collected data based on a plurality ofpre-selected criteria.
 15. The method of claim 12, wherein the indicatorcomprises a data flag that has a first set condition indicating that theevent corresponding to a dangerous condition has occurred and a secondreset condition indicating that the data download has occurred after thelast event corresponding to a dangerous condition.
 16. The method ofclaim 12, wherein the data download corresponds only to data related tothe event corresponding to a dangerous condition.
 17. The method ofclaim 12, wherein the event comprises at least one of: an equipmentmalfunction, a low battery charge reading, and a dangerous medicalcondition.
 18. The method of claim 12, wherein the event comprises atleast one sensed medical condition selected from the group ofventricular fibrillation, ventricular tachycardia, atrial fibrillation,and atrial flutter.